1. Field of the Invention
The present invention relates to a method of making a magnetic head.
2. Related Background of the Invention
With higher recording density of a hard disk drive unit, there is a requirement to further improve the performance of a thin film magnetic head. As the thin film magnetic head, a composite thin film magnetic head, in which a magnetic detection element such as a magneto resistance (MR) effect element and a magnetic recording element such as an electromagnetic coil element are stacked on each other, is widely used, and with these elements, detection of a data signal of a magnetic disk, which is a magnetic recording medium, and writing a data signal to the magnetic disk are carried out.
The factors governing the magnetic detection performance of the thin film magnetic head include a condition called an MR height, which is the height in the direction perpendicular to a medium facing surface of a magneto resistance effect element. This condition affects the magnitude, asymmetry, and the like of a reproduced output of the magneto resistance effect element and thus needs to be controlled precisely as designed.
The adjustment of the size of the MR height is carried out when a wafer, in which thin film magnetic heads are formed in a matrix, is cut for each row called a bar and a lapping process (grinding process) is carried out to the face in which the medium facing surface of this bar is formed. Then, in order to detect the lapping amount in carrying out the lapping process, a plurality of electric lapping guides (ELG, or sometimes called a resistance lapping guide, RLG) is provided in the bar.
Specifically, as described in Japanese Laid-Open Patent Application No. 2003-91804, for example, a plurality of electric lapping guides is arranged opposite to a face, in which the medium facing surface of the bar is formed, and is formed so that the relative positional relationship with the magneto resistance effect element be known in advance. Then, as this medium facing surface is lapped and the MR height becomes smaller, the electric lapping guide is also ground. Accordingly, the height in the direction perpendicular to the medium facing surface of the electric lapping guide also decreases, so that the electric resistance value of the electric lapping guide will vary corresponding to the grinding amount. For this reason, if a change in the magnitude of the electric resistance value of the electric lapping guide is measured during the lapping process and the lapping is finished when it reached a predetermined electric resistance value, the lapping process can be carried out so as to give a predetermined size of the MR height.
However, in the lapping process using the conventional electric lapping guide, the relative positional relationship between the magneto resistance effect element and the electric lapping guide sometimes deviates from a designed relationship and thus the MR height deviates from the design value accordingly.
Specifically, the relative positional relationship between the magneto resistance effect element and the electric lapping guide is basically determined by a reticle pattern which is used in patterning these. However, when the reticle pattern is transferred to photoresist to form a resist pattern, the shape of the resist pattern will shrink or expand slightly as compared with the pattern in the reticle. The degree of this shrinkage or expansion varies depending on the exposure conditions, such as the reflectivity of photoresist, the type of underlayers, and the focusing position at the time of exposure. Since the patterns of the magneto resistance effect element and electric lapping guide are located far away from each other as compared with the size of the magneto resistance effect element, the exposure conditions for the respective resist patterns for patterning the magneto resistance effect element and electric lapping guide sometimes differ, respectively, and the degrees of shrinkage or expansion of these resist patterns sometimes differ, respectively. For this reason, the relative positional relationship between the patterned magneto resistance effect element and electric lapping guide sometimes deviates.
Moreover, it is also known that the degree of shrinkage or expansion of this resist pattern depends on the size and shape of the resist pattern. Usually, the size of the resist pattern for patterning the magneto resistance effect element is on the order of submicron, while the size of the resist pattern for patterning the electric lapping guide is on the order of several tens of microns, and thus both sizes differ, significantly. For this reason, due to the size difference, the relative positional relationship between the patterned magneto resistance effect element and electric lapping guide sometimes shifts further. In particular, in a hard disk drive unit complying with high recording density, the deviation margin allowed for various characteristics of the constituent elements thereof is extremely small, and thus the degree of deviation of the MR height accompanied by the above-described deviation in the relative positional relationship between the magneto resistance effect element and the electric lapping guide might not be allowed.
Accordingly, the present invention is intended to provide a method of making a magnetic head wherein the size of the MR height can be controlled precisely.